1. Field of the Invention
The invention relates to methods and apparatus of physical separation of solids from fluids or for mixing two fluids. More specifically, the invention relates to methods and apparatus for separating solids from fluids and mixing fluids by using a ring having a plurality of grooves through which fluid passes. The methods and apparatus of the present invention are particularly suitable for use in treatment of aqueous fluids, such as water and wastewater, by dynamic separation of contaminants to be removed and by dynamic mixing of treating agents to be added as part of treatment.
2. Description of the Related Art
Commercial and industrial processes currently employ countless operations involving mixing of fluids (liquids with liquids, gases with liquids, and gases with gases) or separation of fluids or solids from other fluids
For example, excessive contaminants must be removed from the wastewater of food service institutions (restaurants, cafeterias, hospitals, etc.) before the water may be discharged. If established discharge-contamination levels are exceeded, cities and other governmental authorities may impose surcharges on the food service institutions. These surcharges increase the costs of doing business.
Typically, food service establishments are required to have grease interceptors, commonly called xe2x80x9cgrease trapsxe2x80x9d, installed in wastewater outlets with sampling wells downstream of the grease traps before the discharge enters the public sewage lines so the authorities can check the discharge from each facility. When the grease traps become full, the contaminants collected in them are removed by vacuum trucks and further treated before discharging to the public sewage.
In addition to the problem of discharging excessive contaminants to public sewage systems, animal fat rendered during the cooking process can congeal when mixed with cold water and clog up the drain lines from the kitchens to the grease traps. When this occurs, the businesses may be shutdown and typically require routing out with a rotor cutter driven by a mechanical cable to open the lines.
Some of the contaminants are destroyed in the grease traps by bacteria. When the contaminants exceed the capacity of what the bacteria can consume, they must be removed from the grease traps by vacuum trucks, or they are discharged to the public sewer, which can result in surcharges as mentioned above.
Bacteria are active only at the limited outer surface of the contaminants to be consumed as food. The bacteria produce enzymes to disperse the contaminants and increase the amount of surface, and the amount of food, available to them. A different enzyme may be required to disperse each contaminant present. When the food is available, bacteria can reproduce in large quantities in very short periods of time. Oxygen dissolved in the water drained into grease traps can become quickly depleted, and aerobic bacteria (those requiring oxygen continuously in order to survive) die. This leaves the task of consuming the contaminants to the anaerobic bacteria (those requiring the absence of oxygen in order to survive). Anaerobic bacteria are not as efficient as aerobic bacteria in consuming the contaminants, and they also produce offensive odors in the process of consuming their food. The offensive odors are prevalent around businesses with grease traps.
Feeding aerobic bacteria in the drain lines from the kitchens has been somewhat successful at either keeping the lines from clogging or increasing the intervals between the times mechanical routing is required. As soon as the aerobic bacteria reaches the grease trap with the oxygen depleted, they die.
Attempts have been made to keep the bacteria alive by bubbling air in grease traps with limited success. Bubbling air even with the finest diffusers creates a large amount of foam in the grease traps. Therefore, air injection has been largely limited to short periods of time and to smaller systems.
Air bubbles rise quickly out of the water, and the bottom of the grease traps return to an anaerobic condition almost immediately preventing the efficient aerobic bacteria from consuming the solids on the bottom of the grease trap. This limits the bubbling of air to the upper part of the grease trap. When oxygen reaches the anaerobic bacteria on the bottom of the grease trap, they die. Therefore, a periodic kill of the anaerobic bacteria on the solids settled on the bottom of the grease trap can be expected. When left for an extended period of time, the solids on the bottom of the grease trap can become packed and act as a seal to prevent oxygen from penetrating into the solids. Only floating contaminants are then consumed by the aerobic bacteria. The offensive odors are also not eliminated.
Therefore, in the food service industry, there is a need for an efficient apparatus and method that can effectively remove particles from wastewater without the problems mentioned above, e.g. incurring surcharges for unsuccessfully meeting contaminant levels, producing offensive odors, requiring the introduction of bubbling air, thus increasing costs, etc.
Another industry faced with the problem of removing contaminants from fluids is the vehicle washing industry. Water used for vehicle washing typically contains significant amounts of suspended solids, dissolved minerals, and organic materials, including oils and other hydrocarbons. Detergents and other chemicals used in the wash operation present further difficulties to the discharge problems. The wash water with the contaminants is typically drained into some type of still pool as a pit or sump. Some of the still pools function as settling basins for the suspended solids and as oil interceptors similar to the grease traps used in food processing facilities.
The water is typically reused in the washing part of the wash cycle until it becomes apparent that the quality of the vehicle wash is no longer satisfactory. Vacuum trucks are then used to remove the contaminants from the sumps and haul them away to disposal sites. Still pools are optimal breeding ground for anaerobic bacteria, which give off a strong and unpleasant odor. The offensive odors are often detected by customers, especially early in the morning when the systems have been shutdown for the night. Bubbling large quantities of air in the still pools can reduce the offensive odors.
The bubbling of air continuously can cause a foaming problem in the sumps. In addition to the offensive odors, governmental regulations may limit the amount of contaminants that can be discharged into the public sewer systems and totally prevent discharge to the environments.
Multiple attempts have been made to improve the process of separating particles from fluid. For instance, U.S. Pat. No. 5,647,977 discloses that the water from vehicle wash facilities can be completely recycled, without water discharge. However, where the cost of water is not a factor and the public sewage system can accept certain contaminants, a complete recycling system may not be cost justified. In such systems, aeration by dissolved oxygen can be used to element the foul odors without the foaming problems typically caused by continuously bubbling air in the sumps. Additional treatment to remove the suspended solids and reduce the organic materials in the sump, other than detergents, can render the water suitable for reuse in the washing part of the vehicle wash cycle, or for discharge where permitted in selected public sewage systems.
Another industry faced with the problem of separation of suspended solid particles from fluids is the water treatment industry. Typically, the solid particles are removed by settling in still pools, centrifugal separation by cyclone filters, and adding flocculating accelerators followed by clarification. Secondary filtration of the fluids often follows the bulk removal operations. The solid particles have to be concentrated and dewatered after separation for disposal. These steps may increase the time and money associated with the particle-removal operation.
An industry having the need to aerate water is the livestock industry. Concentrated animal feeding operations including cattle, swine, poultry, sheep, horses, etc. typically have ponds called xe2x80x9clagoonsxe2x80x9d in which all animal waste is collected. Aeration with dissolved air in water continuously circulating through the lagoons allows naturally occurring bacteria to thrive in the nutrient rich environment of lagoons and greatly accelerate decomposition of the organic waste. Similarly aquatic farms, such as for fish and shrimp, with concentrations of species may require injection of supplementary oxygen in the water to replace oxygen consumed by decaying plants.
To remove contaminants from wastewater, many present applications employ a cyclone filter. A typical cyclone filter is an apparatus that can be used to separate suspended solids from fluids (such as solids from water and air) and to separate fluids of different densities (such as oil and water) by using the centrifugal force caused by a forced spiral vortex. The external force used to generate the spiral vortex in a cyclone filter is typically provided by injecting a stream of a contaminated fluid at high velocity into the filter at one end perpendicular and at a tangent to the cylinder in which the fluid circulation occurs. The axis of circulation in a cyclone filter can be at any angle from vertical to horizontal.
When the axis of circulation is vertical, the direction of the forces of gravity are, therefore, equal around the entire circular path of the fluid. When the axis of circulation is at some angle other than vertical, the design of the cyclone filter has to account for the differences in the direction of the forces of gravity acting on the fluid as it flows while circulating with or against the forces of gravity.
The design of the inlet through which the high velocity fluid is introduced becomes a major factor in the effectiveness of present cyclone filters, especially in the separation of very fine (small) solid particles from fluids.
Present cyclone filters typically have only one inlet through which the fluid and contaminant mixture is introduced. The single inlet may be typically round or rectangular. And in present cyclone filters, the inlet must supply fluid tangentially to the filter. This may lead to difficulties in certain applications.
Several attempts have been made to improve the efficiency and effectiveness of cyclone filters. For instance, U.S. Pat. No. 5,882,530 describes using a cyclone separator in which the lower frustoconical surface contains porous surfaces. The cyclone separator of the ""530 patent may be used for separating a suspension. However, it has been found that over time, particles concentrate along the inner walls of the apparatus as a result of centrifugal forces and tend to clump together and adhere to the porous walls. This clump formation or caking impedes the exit of the carrier fluid through the porous walls.
Other attempts include those disclosed in U.S. Pat. Nos. 5,021,165, 5,478,484, and 6,024,874. However, these attempts generally require the incoming fluid to be tangentially fed into cyclone filter. This limits the use of the filters when tangential feeding is not possible, for example.
Thus, a need exists for an improved apparatus and method of removing particles from fluids. It is desirable that the apparatus and method remove particles at a desired level to reduce the chance of the imposition of a surcharge. It is desirable that the method should not increase costs or increase time involved in removing the particles. An apparatus that does not have to input the fluid tangentially is desired. A need also exists for an improved method of mixing fluids or aerating fluids in a timely fashion.
It will become clear to those skilled in the art having the benefit of this disclosure that the methods and apparatus in accordance with he present invention overcome, or at least minimize, the deficiencies of existing mixing apparatus and methods.
The present invention provides a new method and apparatus for separation of suspended solids from aqueous fluids, for separation and mixing of fluids, and for dissolving gases in aqueous fluids. An apparatus in accordance with one embodiment of the present invention may employ a grooved ring to divide the fluid stream and impart a high velocity on each of the divided streams. A grooved ring with any number of grooves that may be spiraled may be employed to create a high velocity circular motion on the divided stream for separation of suspended solid particles by centrifugal force in a cyclone filter and for saturation of liquids with gases in a fluid mixer where gases are introduced through a diffuser.
A grooved ring with any number of grooves, that may be radial, is described in another embodiment as fluid mixer to divide a stream of fluid, produce a high velocity flow through each groove, introduce a second fluid through an orifice into the first fluid flowing through each groove, and direct the fluid mixture to a center impact zone where the various streams collide to complete the mixing.
Another embodiment of a cyclone filter of the present invention consists of a spiral-grooved ring inlet, a down-flow annulus between a long outer cylinder and a short inner cylinder, a wider solid particle collection chamber below the long cylinder, a fluid interceptor positioned just below the long cylinder in the collection chamber, and a vortex finder and outlet in the inside diameter of the short inner cylinder of the annulus. Fluid contaminated with solid particles may enter the cyclone filter and may be divided to flow through any number of spiral grooves in the spiral-grooved ring then injected at high velocity around the circumference of the down-flow annulus to spiral downward.
The solid particles migrate to the outside of the circulating stream and are separated from the fluid at the bottom of the long cylinder as the flow is reversed by the interceptor to flow upward in the low pressure center of the circulating stream to the vortex finder and out the top of the filter.
Another embodiment of a cyclone filter of the present invention consists of a spiral-grooved ring inlet, a housing having an upper cylinder and a lower cone, a vortex finder and fluid outlet in the top center of the upper cylinder, and a solid particle outlet at the bottom of the cone. The spiral-grooved ring inlet is positioned outside the upper cylinder. Fluid contaminated with solid particles enters the cyclone filter and flows through the grooves in the spiral-grooved ring then injected at high velocity in a number of streams around the circumference and at a tangent to the top inside diameter of the upper cylinder creating a centrifugal force to drive the solid particles against the inside diameter of the upper cylinder and lower cone as it spirals downward. The solid particles continue to flow downward and are separated from the fluid and out the bottom of the cone as the fluid flow is reversed by the decreasing area of the cone to flow upward in the low pressure center of the circulating stream to the vortex finder and out the top of the filter.
Another embodiment of a cyclone filter of the present invention has the same housing with the spiral-grooved ring on the outside as the embodiment described above with a narrow annulus added just inside the upper cylinder with the incoming fluid injected in multiple high velocity streams into the annulus to spiral downward to exit the annulus in the lower part of the cylinder away from the outlet as a narrow high velocity stream against the cylinder wall. The narrow annulus eliminates the need for a vortex finder as part of the outlet in many applications.
Another embodiment of a cyclone filter of the present invention has a grooved ring mounted inside the narrow annulus around the outlet on large cyclone filters with the fluid injected from the inside outward into the annulus.
A fluid mixer is described. In one embodiment the fluid mixer of the present invention is applied as a dissolved gas generator consisting of a cylinder used as the housing, a spiral-grooved ring liquid inlet located on the outside near the top of the cylinder, an inverted cone gas diffuser mounted in the center of the cylinder below the level of the spiral-grooved ring inlet, a gas inlet to the diffuser, an excess gas outlet in the top of the cylinder, and a saturated fluid outlet in the bottom of the cylinder. The liquid enters the fluid mixer and flows through the grooves of the spiral-grooved ring then injected at high velocity in a number of streams around the circumference of the cylinder creating a circular flow above the inverted cone diffuser with a vortex at its center. The circulating liquid flows downward around the inverted cone diffuser and intercepts and dissolves the gas distributed through the diffuser as it flows upward. The liquid saturated with the gas continues to flow downward and out of the fluid mixer through the bottom outlet. The excess gas flows upward past the inverted cone diffuser and is separated from the liquid in the vortex and released to atmosphere from the top of the fluid mixer.
Another embodiment of the fluid mixer of the present invention is also applied as a dissolved gas generator consisting of an upper housing, an orifice ring, a radial-grooved ring, and a lower cylinder with a cap. The upper housing has a liquid inlet, a gas inlet, an excess gas separation zone, and an excess gas outlet. The orifice ring and the radial-grooved ring are mounted inside the upper housing with the orifice ports in the orifice ring positioned over the grooves in the radial-grooved ring. Liquid enters the fluid mixer and flows through the grooves in the radial-grooved ring where gas is injected through the orifice ring into each of the high velocity streams. The liquid-gas mixture stream in each groove is injected into the impact zone to collide with each other. The liquid becomes saturated and flows downward into the lower cylinder where the excess gas forms bubbles and flows upward to return to the impact zone. The saturated liquid exits through the bottom of the fluid mixer. The excess gas flows to the gas separation zone above the impact zone, separated from the liquid, and released to atmosphere.
Another embodiment of the fluid mixer of the present invention is used for mixing liquids, for mixing gases, and for mixing liquids and gases where excess gases do not have to be separated from the liquids. The fluid mixer consists of an upper housing, an orifice ring, a radial-grooved ring, and a short cylinder with a cap. The center of the radial-grooved ring serves as an impact zone to which the streams are directed. The first fluid enters the fluid mixer and flows through the grooves in the grooved ring where a second fluid is injected through the orifice ring into each of the high velocity streams. The fluid mixture in each of the radial grooves is then injected at high velocity into the impact zone to collide with each other and become completely mixed. The fluid mixture flows downward out of the impact zone into the lower cylinder and out the bottom of the fluid mixer.
Another embodiment of the fluid mixer of the present invention is also used for mixing liquids, for mixing gases, and for mixing liquids and gases where excess gases do not have to be separated from the liquids. The fluid mixer consists of an upper housing, a radial-grooved ring, a combination venturi-orifice ring positioned with the venturi and orifice ports in each groove of the radial-groove ring in order to draw by suction a second fluid into each stream, and an impact zone to complete the mixing of various fluids.